1. Technical Field
The invention is related to morphing three-dimensional objects represented by light fields, and in particular, to a system and method for image-based three-dimensional morphing and texture transfer based on a correspondence between rays of source and target light fields.
2. Related Art
Metamorphosis, or morphing, is a popular technique for creating visual effects. In general, image morphing is the construction of an image sequence depicting a gradual transition between two images. Thus, when used effectively, morphing can produce a compelling illusion that an object is smoothly transforming from one object into another. Morphing two-dimensional (2D) images simply morphs the images themselves. However, when morphing images represented by three-dimensional (3D) models, intermediate 3D models; i.e., “morphs” are typically generated directly from the given models rather than simply morphing the images themselves. These morphs are then rendered to produce a morphed image sequence depicting a transformation from a source 3D model to a target 3D model.
With conventional 3D morphing schemes, creating the morphs is independent of the viewing and lighting parameters. Consequently, a single morph sequence can be created then rendered with various camera angles and lighting conditions during rendering. This differs from the 2D morphing approach where a new morph must be recomputed every time it is desired to alter the viewpoint or the illumination of the morphed view.
A variety of conventional schemes for morphing 3D objects have been proposed. Many such schemes are designed for geometry-based objects, i.e., objects whose geometry and surface properties are known, either explicitly as with conventional boundary-based techniques, or implicitly as with conventional volume-based techniques. In either case, such techniques typically rely on a three-dimensional mesh-type model of the objects being morphed. Unfortunately, where the geometry is unknown or difficult to model, such conventional 3D morphing schemes fail to create realistic morphs.
Volume-based 3D morphing schemes typically based on the concept of “volume morphing.” Volume morphing schemes typically use a source and a target volume for creating morphs. Volume data used by such schemes is typically acquired by a number of techniques, including scanning, voxelizing a geometric model, interactive modeling, or procedurally defining hypertexture volumes as functions over 3D space. However, such methods either require extensive user input or interaction, or are very computationally expensive, or both.
Another scheme approaches 3D morphing using a technique termed “plenoptic editing.” This scheme first recovers a 3D voxel model from the image data and then applies traditional 3D warping to the recovered model. Visibility issues can be resolved with the recovered geometry, but there are problems, including a Lambertian surface assumption needed for voxel carving, and fundamental difficulties associated with recovering detailed surface geometry from images. Further, Lambertian surface patches are idealized and assumed to have a constant luminance value. Consequently, the use of Lambertian surfaces fails to consider specular components to the reflected spectrum that exists on real, or non-Lambertian, surfaces. Such real, or non-Lambertian, surfaces typically exhibit specular characteristics that are not adequately modeled by this plenoptic editing scheme.
Therefore, what is needed is a system and method for morphing 3D objects without the need to explicitly consider object geometry. Further, such a system should both minimize user interaction and be computationally efficient. Finally, such a system and method should be capable of effectively morphing objects that include non-Lambertian and other specular surfaces.